Error Detection and Reporting
EAC Internal Checkers
Data Parity Checkers
All the microcode (DMA layer, CSP layer) and data are checked for parity when the
EAC internal buffers are read or written.
Reporting
When any of the above checkers becomes active:
The EAC:
– Stores the corresponding error condition in an error register.
– Interrupts the CSP microcode at level 0.
The CSP Microcode:
– Provides a level 1 status to the control program.
Error Status
The error status is provided as the LA or L-STAT field in some ESS 08 type BERs.
Refer to Chapter 11.
Four types of error may be reported:
Type 1
Error detected by the CCU during PIO. A halt is send to the CSP,
which results in a CCU or MOSS level 1 interrupt.
Type 2
Error detected by the CCU during AIO. A halt is send to the CSP,
which results in a CCU or MOSS level 1 interrupt.
Type 3
Internal logical errors detected by the CSP microcode. A CCU level 1
or MOSS level 4 interrupt is set.
Hard Stop
A CSP microprocessor check has been encountered. The CSP hard-
ware responds with the error status.
The following tables show the detailed responses that may be presented to a get
error status command:
Error Status Byte ð
┌───────────┬────────────────┬──────────────────┬───────────────────────┐
│ Bit
│
│
│
│
│ ð123 4567 │ Type 1
│ Type 2
│ Type 3
│
├───────────┼────────────────┼──────────────────┼───────────────────────┤
│ x... .... │ R/W (IOH)
│ R/W (AIO)
│ Always ON
│
│ .x.. .... │ I/O bus check
│ I/O bus check
│ Invalid level ð int.
│
│ ..x. .... │ Not used
│ Cycle steal grant│ Invalid level 1 int.
│
│ ...x .... │ I/O bus tag I/O│ I/O bus tag I/O
│ Invalid level 2 int.
│
│ .... x... │ Halt
│ Halt
│ Microcode check
│
│ .... .x.. │ TA
│ Not used
│ CS/CCU L2 stack overf.│
│ .... ..x. │ TD
│ TD
│ Reject: command on cmd│
│ .... ...x │ Not used
│ Not used
│ Disconnect state
│
└───────────┴────────────────┴──────────────────┴───────────────────────┘
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IBM 3745 Models 130, 150, 160, 170, and 17A: Hardware Maintenance Reference
Summary of Contents for 3745 Series
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